The long term goal of this project is to understand the molecular basis of globin gene switching in rabbit development. This project relates to the human diseases Alpha- and Beta-thalassemia, which result from impaired expression of Alpha- or Beta-globin, and to sicklecell anemia and some other hemoglobinopathies which may be cured or alleviated by switching fetal or embryonic globins back on in adult life. In a larger context, this project addresses fundamental questions about gene regulation in development, which could provide new insights into the many intractable diseases that can be described as aberrations in development, e.g. muscular dystrophy, cystic fibrosis, and diabetes. Our specific aims are to: 1) compare the known rabbit Beta-globin gene sequences with those from other mammals to test a model for mammalian globin evolution, 2) determine the transcription unit for the adult Beta-globin gene, 3) examine aspects of chromatin structure that could be responsible for the transcriptional control of the Beta-globin family by cloning the genes into mouse cells via a bovine papilloma virus (BPV) episome to amplify the signals from active genes and aid in purification of a minichromosome, 4) measure the stability of the embryonic Beta-globin mRNAs in the BPV-globin recombinant clones, 5) examine the efficiency of each of the genes in an in vitro transcription system with and without reconstitution into chromatin, and 6) test for gene-specific binding proteins in erythroid nuclei. Other projects are to 7) isolate and characterize the rabbit Alpha-like globin gene family and 8) complete the characterization of a repeated sequence family in rabbits and test for developmental regulation.